Fuel-Economy Performance Analysis with Exhaust Heat Recovery System on Gasoline Engine

As the electrification and connectivity technologies penetrate the market, the opportunities for intelligent thermal management of the vehicles become more salient. When an exhaust gas heat recovery (EGHR) system is used to recover waste heat from gasoline engine exhaust, the thermal parameters of the exhaust gas vary greatly, and these influence the performance of the heat exchanger (HE) system. To improve the recovery of exhaust waste heat and its conversion to faster coolant warm-up and cabin heating performance effectively, the heat transfer evaluation and optimal performance analysis are conducted on different EGHR system designs with different exhaust thermal parameters. This study aims at analyzing the fuel economy benefit with state-of-the-art HE designs in the automotive industry for exhaust gas-to-oil and exhaust gas-to-coolant heat transfer. Both physical testing and virtual simulation helped us develop a method to take advantage of the exhaust gas heat. The test result indicates that with the integration of the exhaust gas-to-coolant and exhaust gas-to-oil HEs, the gasoline engine makes a 0.5% and 0.8% fuel efficiency improvement, respectively. More specifically, the Worldwide harmonized Light vehicles Test Cycles (WLTC) fuel consumption on the 1.0L engine can be reduced by 0.5% with the integration of exhaust gas to the coolant HE, which has a smart bypass control strategy upstream of the oil cooler. Also the implementation of exhaust gas-to-oil HEs leads to a WLTC fuel consumption reduction of 0.8%. HE design with bypass valve and valve-controlled oil cooler from the experiments proved to be the most efficient HE design among the four investigated designs. The proposed simulation-based performance and engine dynamometer (dyno) evaluation shed light on the importance of selecting bypass valve and valve-controlled oil cooler HEs and design-related improvements in fuel economy for practical applications in building intelligent thermal management for vehicles.